Some wireless communications devices have Global Positioning System (GPS) chipsets (or external Bluetooth™ accessories) that convert radio-frequency signals received from orbiting GPS satellites into real-time coordinates of longitude and latitude that are typically accurate to within a few meters of the actual current location of the device. The current location (i.e. the coordinates of longitude and latitude) can then be transmitted wirelessly to a recipient who has another wireless communications device (or via cellular base station and Internet to any other networked computing device) to thereby enable the recipient to map the coordinates using any one of a number of available mapping applications such as BlackBerry Maps™, Google Maps or TeleNav™. Transmitting the GPS-determined current location from one mobile device to another enables two mobile users to rendezvous or alternatively enables one mobile user to follow another mobile user. This sort of “consensual” tracking is described, for example, in PCT Publication WO 2006/108071 (X ONE, Inc.) entitled “Location Sharing and Tracking Using Mobile Phones or Other Wireless Devices”. In a similar vein are covert GPS tracking devices that are meant to be attached to a target's vehicle without the knowledge and consent of the target. These covert devices provide only static location updates, either automatically (i.e. periodically) or upon remote request. See, for example, U.S. Patent Application Publication 2007/0139223 (Bedenko) entitled “Vehicle Tracking System” and U.S. Patent Application Publication 2007/0099626 (Lawrence et al.) entitled “Tracking System and Method”.
Consider the (“consensual”) scenario whereby a first mobile user wants a second mobile user to follow him. The first mobile user can periodically send his GPS coordinates to the second mobile user to thus enable the second mobile user to plot the static position data using a mapping application. However, due to the time lag in generating, transmitting and mapping the position data, by the time the second mobile user sees the “current” location of the first mobile user, the location is no longer “current”. This is particularly problematic when the second mobile user is following the first mobile user at high speed, such as in their respective cars or other vehicles, in which case the time lag between updates may make it difficult to follow the first mobile user. This problem is further exacerbated in densely populated urban areas where the density of roads makes it less apparent which route or routes need to be taken in order to reach the most recently received location update of the first mobile user. Although one solution might appear to entail more frequent position updates, this would undesirably burden the onboard processors of both the sender's and recipient's devices, not to mention using up valuable wireless bandwidth with the extra over-the-air transmissions. An improvement to this prior-art technology would thus be highly desirable in order to facilitate the tracking of one mobile user by another.
It will be noted that throughout the appended drawings, like features are identified by like reference numerals.